This invention relates to an improved hydrocarbyl-substituted succininc anhydride/nonionic emulsifier composition. This invention also relates to an improved method for imparting water repellency to surfaces containing groups reactive to anhydrides. A further aspect of this invention relates to an improved method for the sizing of paper and paperboard products.
It is well known in the art that hydrocarbyl-substituted succinic anhydrides are good for treating paper, fabric, or other surfaces to impart water repellency. As indicated in U.S. Pat. Nos. 3,102,064, 3,821,069, 3,968,005, and 4,040,900 (RE 29,960), these compositions are particularly useful for sizing paper.
It is also known that these succinic anhydrides are best applied for such purposes in a highly dispersed form, such as an aqueous emulsion. See, for example, U.S. Pat. No. 4,040,900 (RE 29,960), which describes paper sizing emulsions made from mixtures comprising a substituted cyclic dicarboxylic acid anhydride and polyoxyalkylene alkyl or alkylaryl ether or the corresponding mono- or di-ester.
Diester emulsifiers, as well as monoesters, alkyl phenol ethoxylates and alcohol ethoxylates, are disclosed in U.S. Pat. No. 4,040,900 (RE 29,960) as useful emulsifiers for substituted succinic anhydrides. This patent teaches that the polyoxyalkylene portion of the emulsifier must contain between 5 and 20 polyoxyalkylene groups. For polyoxyethylene (polyethylene glycol) type emulsifiers, this corresponds to a molecular weight range of about 238 to 899.
A major drawback of these prior art emulsifiers is the fact that, once formed, the succinic anhydride-emulsifier mixtures are unstable and must be promptly used. There therefore exists a need in the art for substituted succinic anhydride-emulsifier mixtures which demonstrate enhanced stability upon aging or storage.